Parameters which normally are to be taken into account when designing disposable medicament delivery devices include measures to render it difficult to reuse the device and measures to protect users from needle sticks.
US2007/0191809 discloses a passive needle guard comprising a body, a shield covering the body and a spring disposed between the body and the shield. A needle can be mounted to the body at the proximal end thereof, i.e. at the end facing the user of the device during use. The body is arranged to receive a syringe for administration of a medicament. The spring biases the shield from the proximal end of the needle guard towards the distal end of the needle guard. A catch acts to retain the shield in the biased position. When the plunger reaches its final position, the thumb pad of the plunger releases the catch wherein the shield moves relative the body such that the proximal end of the body moves towards the distal end of the shield. The needle is thus received by the shield. The shield is locked in this position relative the body by means of a locking member which consists of a proximal end tab of the body engaging with an inner surface slot at the distal end of the shield.
A problem with existing solutions is however that the needle is not covered prior to administration of the medicament if the needle shield which normally covers the needle has been removed. Moreover, US2007/0191809 allows for the removal of the plunger post administration, which could render it possible to reuse the syringe.